Ethylene/alpha-olefin copolymer made with a non-single-site/single-site catalyst combination, its preparation and use

ABSTRACT

An ethylene/α-olefin copolymer comprising a component produced by a non-single-site polymerization catalyst and a component produced by a single-site polymerization catalyst, its preparation and use are described. The copolymer has an α-olefin content of 5 to 20 percent by weight aud shows at least two CRYSTAF peak temperatures differing by at least 15° C. and/or at least two DSC melting peak temperatures differing by at least 15° C.

This application claims the benefit of U.S. Provisional Application No.60/334,566 filed Nov. 30, 2001, the entire disclosure of which is herebyincorporated by reference.

FIELD OF THE INVENTION

The present invention relates to an ethylene/α-olefin copolymer madewith a non-single-site/single-site polymerization catalyst combination.The present invention also relates to a process for making such acopolymer and to articles made therefrom, such as, e.g., blown film.

DISCUSSION OF BACKGROUND AND OTHER INFORMATION

It is well known in the field of film production that the modulus orstiffness of a resin film increases with increasing resin density.Correspondingly, lower resin density usually results in increased impactand tear strengths. In the case of films of resins made by conventionalZiegler catalysts (which are typical examples of non-single-sitepolymerization catalysts) alone, improving the stiffness of a filmconstruction, a requirement for many industrial and packaging films,entails inevitable tradeoffs, i.e., increased density to improvestiffness typically sacrifices impact and tear strengths.

Lower haze and higher gloss are other film attributes that improve withlower resin density. If both haze and gloss as well as stiffness of afilm are to be optimized, another compromise has to be made withconventional Ziegler catalyzed resins. Therefore, it would be desirableto have available a resin, in particular, a polyethylene resin whichdespite a relatively low density and favorable film propertiesassociated therewith such as, e.g., high impact and tear strengths(toughness) as well as low haze and high gloss, shows a modulus(stiffness) that renders the films made therefrom suitable forapplications such as industrial and packaging film.

U.S. Pat. No. 6,051,525 to Lo et al., the disclosure of which isexpressly incorporated herein by reference in its entirety, discloses acatalyst composition for preparing a high activity catalyst supported onsilica which produces, in a single reactor, polyethylene with a broad orbimodal molecular weight distribution. The catalyst is prepared from theinteraction of calcined silica with dibutylmagnesium, 1-butanol andtitanium tetrachloride and a solution of methylalumoxane andethylenebis[1-indenyl]zirconium dichloride.

U.S. Pat. No. 5,539,076 to Nowlin et al., the disclosure of which isexpressly incorporated herein by reference in its entirety, disclosesresins which are in situ catalytically produced polyethylene resinblends of a broad bimodal MWD that can be processed into films onexisting equipment and exhibit good processability in blown filmproduction, reduced tendency towards die-lip buildup and smoking inon-line operations. The preferred catalyst for producing these resinscomprises a catalyst including a support treated with a dialkylmagnesiumcompound, an aluminoxane, at least one metallocene and a non-metallocenetransition metal source as well as an alkylaluminum compound ascocatalyst.

U.S. Pat. No. 5,614,456 to Mink et al., the disclosure of which isexpressly incorporated herein by reference in its entirety, is directedto an activated catalyst composition for producing bimodal MWD highdensity and linear low density polyethylene resins, which activatedcatalyst does not require alkylaluminum cocatalyst. A preferred catalystcomprises, as support, silica impregnated with a dialkylmagnesiumcompound and an organic alcohol reagent, e.g., butanol. Said support iscontacted with at least two transition metal compounds, at least one ofwhich is a metallocene, and, as activator, aluminoxane, either alone oradmixed with metallocene compound.

Other background references include EP 0 286 177, EP 0 643 084,Kyung-Jun Chu et al., “Variation of molecular weight distribution (MWD)and short chain branching distribution (SCBD) of ethylene/1-hexenecopolymers produced with different in-situ supported metallocenecatalysts,” Macromol. Chem. Phys. 201 (2000), 340-348, and literaturecited therein, C. Gabriel et al., “Comparison of different methods forthe investigation of the short-chain branching distribution of LLDPE,”Polymer 42 (2001) 297-303, and literature cited therein, and J D. Kim etal., “Copolymerization of Ethylene and 1-Hexene with SupportedMetallocene Catalysts: Effect of Support Treatment, Macromol. RapidCommun. 20 (1999), 347-350, and the literature cited therein.

SUMMARY OF THE INVENTION

The present invention provides an ethylene/α-olefin copolymer which whenformed into products such as film not only shows properties attributableto its relatively low density, in particular, high impact strength, hightear resistance and high clarity, but also provides a degree ofstiffness which usually can only be found in products made from resin ofsignificantly higher density.

The present invention provides an ethylene/α-olefin copolymer comprisinga first component produced by a catalyst derived from a non-single-sitepolymerization catalyst and a second component produced by a single-sitepolymerization catalyst. The weight ratio of the first component and thesecond component ranges from about 9:1 to about 19 and the copolymer hasan α-olefin content of about 5 to about 20 percent by weight.Furthermore, the copolymer shows at least two CRYSTAF peak temperatureswhich differ by at least about 15° C., preferably by at least about 20°C., more preferably by at least about 25° C., e.g., at least about 30°C. Additionally or alternatively, the copolymer shows at least two DSCmelting peak temperatures which differ by at least about 15° C.,preferably by at least about 20° C.

Preferably, the copolymer shows at least one DSC melting peaktemperature in the range from about 115° C. to about 135° C. and/or atleast one CRYSTAF peak in the temperature range from about 75° C. toabout 95° C.

In another aspect, the weight ratio of the first component and thesecond component ranges from about 8:2 to about 2:8, for example, fromabout 7:3 to about 3:7.

In yet another aspect, the copolymer has an α-olefin content of at leastabout 7 weight percent, for example, at least about 10 weight percent orat least about 15 weight percent.

In still another aspect, the CL-olefin comprises 3 to about 12 carbonatoms and may, for example be selected from one or more of propene,1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octeneand 1-decene. A preferred α-olefin is 1-hexene.

In another aspect, the copolymer has a density of not more than about0.93 g/cm³, for example, not more than about 0.925 g/cm³, or even notmore than about 0.92 g/cm³.

In another aspect, the copolymer has an essentially unimodal molecularweight distribution.

In yet another aspect, the copolymer has been produced in a singlereactor.

In still another aspect, the non-single-site polymerization catalyst isderived from at least one compound selected from Ti and V compounds.

In another aspect, the single-site polymerization catalyst is derivedfrom at least one metallocene transition metal compound which may forexample be selected from Ti, Zr and Hf compounds, preferably, ametallocene transition metal compound of the general formula (II)CP_(x)MA_(y)  (II)wherein x is at least 2, M is selected from zirconium and hafnium, Cp isselected from optionally substituted cyclopentadienyl and optionallysubstituted cyclopentadienyl that is part of an aromatic polycyclic ringsystem, provided that at least one Cp is cyclopentadienyl that is partof an aromatic polycyclic ring system, two cyclopentadienyl moieties maybe linked by a bridging group, A is selected from halogen, hydrogen,hydrocarbyl and combinations thereof, and the sum (x+y) is equal to thevalence of M.

In preferred compounds of formula (II), M represents zirconium and/orthe aromatic polycyclic ring system is selected from optionallysubstituted indenyl and optionally substituted fluorenyl and/or x is 2and the Cp groups are linked by a bridging group, e.g., a bridging groupincluding at least one silicon atom. Preferred embodiments of themetallocene transition metal compound of formula (II) includeethylenebis(indenyl)-zirconium dichloride and dimethylsilyl(cyclopentadienyl)(fluorenyl)zirconium dichloride.

In another aspect, the metallocene transition metal compound may be usedin combination with an alumoxane.

The present invention also provides an ethylene/1-hexene copolymercomprising a first component produced by a non-single-sitepolymerization catalyst derived from a titanium compound and a secondcomponent produced by a single-site polymerization catalyst derived froma zirconium metallocene compound. The copolymer has a 1-hexene contentof about 6 to about 12 percent by weight and the weight ratio of thefirst component and the second component ranges from about 7:3 to about3:7. Furthermore, it shows at least two CRYSTAF peak temperatures whichdiffer by at least about 20° C. and at least two DSC peak temperatureswhich differ by at least about 20° C. The density of the copolymer isnot higher than about 0.925 g/cm³, and the zirconium metallocenecompound comprises two bridged cyclopentadienyl rings, at least one ofsaid cyclopentadienyl rings being part of an indenyl or fluorenylmoiety. Also, the copolymer is produced in a single reactor.

The present invention furthermore provides a process for making theabove copolymers. This process comprises contacting, in a singlereactor, ethylene and α-olefin under polymerization conditions and inthe presence of hydrogen with a catalyst combination comprising at leastone non-single-site polymerization catalyst and at least one single-sitepolymerization catalyst.

In one aspect, the single-site polymerization catalyst is derived fromat least one metallocene transition metal compound.

In another aspect, the catalyst combination is used together with analkylaluminum cocatalyst.

In yet another aspect, the catalyst combination comprises a support suchas, e.g., silica.

Furthermore, the process may be carried out continuously. Preferably, itis carried out in the gas phase or as slurry polymerization.

The present invention also provides an article made from the abovecopolymer, for example a blown or extruded article such as a film,including a multilayer film having a thickness of, for example, about0.2 to about 10 mils. Also, the copolymer may contain up to 20 ppmtransition metal derived from the deactivated catalyst.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

The particulars shown herein are by way of example and for purposes ofillustrative discussion of the embodiments of the present invention onlyand are presented in the cause of providing what is believed to be themost useful and readily understood description of the principles andconceptual aspects of the present invention. In this regard, no attemptis made to show structural details of the present invention in moredetail than is necessary for the fundamental understanding of thepresent invention, the description making apparent to those skilled inthe art how the several forms of the present invention may be embodiedin practice.

All percent measurements in this application, unless otherwise stated,are measured by weight based upon 100% of a given sample weight. Thus,for example, 30% represents 30 weight parts out of every 100 weightparts of the sample.

Also, unless otherwise stated, a reference to a compound or component(e.g., the metallocene compounds used in the process of the presentinvention) includes the compound or component by itself, any of itsindividual stereoisomers (e.g., rac and meso) and any mixtures thereof,as well as any combination with other compounds or components, such asmixtures of compounds.

Further, when an amount, concentration, or other value or parameter, isgiven as a list of upper preferable values and lower preferable values,this is to be understood as specifically disclosing all ranges formedfrom any pair of an upper preferred value and a lower preferred value,regardless whether ranges are separately disclosed. Moreover, the upperand lower values of any two or more ranges given for a specificparameter are to be understood as also disclosing the ranges formed bycombining the lower value of a first range with the upper value of asecond range and vice versa.

The term “non-single-site polymerization catalyst” is to denote apolymerization catalyst which comprises more than one catalyticallyactive site. Typical examples of such non-single-site polymerizationcatalysts are the conventional Ziegler catalysts, for example thosederived from Ti and V compounds.

The term “single-site polymerization catalyst”, on the other hand is todenote a polymerization catalyst which comprises essentially only onecatalytically active site. Typical examples of such catalysts arecatalysts based on transition metal metallocene compounds, in particularthose of Ti, Zr and Hf. However, there are many other single-sitepolymerization catalysts which may be employed according to the presentinvention and are well known to those of skill in the art. Illustrative,non-limiting examples thereof can be found in the literature, see, e.g.,G. J. P. Britovsek et al., “The Search for New-Generation OlefinPolymerization Catalysts: Life beyond Metallocenes”, Agnew. Chem. Int.Ed. 38 (1999), 428-447, and literature cited therein, G. G. Hlatky,“Heterogeneous Single-Site Catalysts for Olefin Polymerization”, Chem.Rev. 100 (2000), 1347-1376, and literature cited therein, as well as S.D. Ittel et al., “Late-Metal Catalysts for Ethylene Homo- andCopolymerization”, Chem. Rev. 100 (2000), 1169-1203, and literaturecited therein. All of these publications are fully incorporated hereinby reference. Additional examples of single-site polymerizationcatalysts are based on boracenes, salicylamidine metal complexes,organo-chromium compounds etc. See also the patent literature, forexample, U.S; Pat. Nos. 6,294,626; 6,291,386; 6,265,504; 6,255,415;6,239,062; 6,232,260; 6,228,959; 6,204,216, 6,180,552; and 6,114,270,all fully incorporated herein by reference. Further examples ofsingle-site polymerization catalysts suitable for use in the presentinvention will be apparent to those skilled in the art.

Transition metal metallocene-based catalysts are a preferred class ofsingle-site polymerization catalysts for use in the present invention.Therefore, for the sake of convenience the following description willexclusively refer to this preferred class of single-site polymerizationcatalysts. It must be kept in mind, however, that thesemetallocene-based catalysts may be replaced by any of the othersingle-site polymerization catalysts known in the art.

A preferred synthesis of a catalyst combination useful for thepreparation of the ethylene/α-olefin copolymer of the present inventioncomprises two stages, synthesis of a supported catalyst intermediate(preferably in the given order of consecutive steps and withoutisolation of a dry product until after the incorporation of thetransition metal compound for forming the non-single-site polymerizationcatalyst) and synthesis of the final supported catalyst combination.Thus the synthesis is preferably carried out in a series of severalconsecutive steps under inert conditions in the substantial absence ofwater and molecular oxygen.

According to said preferred synthesis, support material is firstslurried in a non-polar solvent. Support materials for preparing thecatalyst combinations for use in the present invention comprise solid,particulate, porous materials and may include support materialsdisclosed in U.S. Pat. No. 4,173,547, the disclosure of which isexpressly incorporated herein by reference in its entirety. Such supportmaterials include, but are not limited to, metal oxides, hydroxides,halides or other metal salts, such as sulfates, carbonates, phosphates,silicates, and combinations thereof, and may be amorphous andcrystalline. Some preferred support materials include silica, aluminaand combinations thereof. Support material particles may have any shape,and are preferably approximately spherical (such as obtainable, e.g., byspray-drying).

Preferred support materials comprise particles, the optimum size ofwhich can easily be established by one of ordinary skill in the arthaving the benefit of the present disclosure. A support material that istoo coarse may lead to unfavorable results, such as low bulk density ofthe resulting polymer powder. Thus, preferred support materials compriseparticles with average size, e.g., diameter, smaller than about 250 μm,more preferably smaller than about 200 μm, most preferably smaller thanabout 80 μm. Preferred support materials comprise particles larger thanabout 0.1 μm, more preferably larger than about 10 μm in size, becausesmaller silica particles may produce small polymer particles (fines)which may cause reactor instability.

Support material is preferably porous, as porosity increases the surfacearea of the support material, which, in turn, provides more sites forreaction. The specific surface areas may be measured in accordance withBritish Standards BS 4359, volume 1(1969), fully incorporated herein byreference in its entirety. The specific surface area of support materialused for the purposes of the present invention is preferably at leastabout 3 m²/g, more preferably at least about 50 m²/g, and mostpreferably at least about 150 m²/g, e.g., about 300 m²/g. The specificsurface area of support material is generally less than about 1500 m²/g.

The internal porosity of support material may be measured as the ratiobetween the pore volume and the weight of the material and can bedetermined by the BET technique, such as described by Brunauer et al.,J. Am. Chem. Soc., 60, pp. 209-319 (1938), fully incorporated herein byreference in its entirety. The internal porosity of support material ispreferably larger than about 0.2 cm³/g, more preferably larger thanabout 0.6 cm³/g. As a practical matter, the support material internalporosity is limited by particle size and internal pore diameter. Thus,internal porosity generally is less than about 2.0 cm³/g.

Preferred support materials for use in the present invention comprisesilica, particularly amorphous silica, and most preferably high surfacearea amorphous silica. Such support materials are commercially availablefrom a number of sources, and include a material marketed under thetradenames of Davison 952 or Davison 955 by the Davison ChemicalDivision of W. R. Grace and Company or Crosfield ES70 by CrosfieldLimited (surface area=300 m²/g; pore volume 1.65 cm³/g). The silica isin the form of spherical particles, which are obtained by a spray-dryingprocess. As procured, theses silicas are not calcined (dehydrated).

Because the catalyst starting materials used in the preparation of thecatalyst combinations for use in the present invention may react withwater, the support material should preferably be substantially dry.Water that is physically bound to the support material, therefore, ispreferably removed, such as by calcination, prior to forming anon-single-site/single-site catalyst combination for use in the presentinvention.

Preferred calcined support materials comprise support material that hasbeen calcined at a temperature higher than about 100° C., morepreferably higher than about 150° C., even more preferably higher thanabout 200° C., e.g., higher than about 250° C. As sintering of thesupport material is preferably avoided, calcination is preferablyeffected at a temperature that is below the sintering temperature of thesupport material. In one embodiment, calcination of a support material,e.g., silica, is carried out at a temperature of not higher than about950° C. In another embodiment, calcination of a support material iscarried out at a temperature of not higher than about 850° C. In yetanother embodiment, calcination of a support material is carried out ata temperature of not higher than about 650° C. Total calcination timesusually are not shorter than about 4 hours, preferably not shorter thanabout 6 hours, whereas calcination times longer than 24 hours usuallyoffer no particular advantage.

Calcination of support material can be performed using any procedureknown to those of ordinary skill in the art. A preferred method ofcalcination is disclosed by T. E. Nowlin et al., AZiegler-NattaCatalysts on Silica for Ethylene Polymerization,@ J. Polym. Sci., PartA: Polymer Chemistry, Vol. 29, 1167-1173 (1991), the disclosure of whichis expressly incorporated herein by reference in its entirety.

As used in this disclosure, support material as used in the Examplesbelow may, for example, be prepared as follows. In a fluidized-bed,silica (e.g., Davison 955), is heated in steps from ambient temperatureto the desired calcining temperature (i.e., 600° C.). The silica ismaintained at about this temperature for about 4 to about 16 hours,whereafter it is allowed to cool to ambient temperature. The calcinationtemperature primarily affects the number of OH groups on the supportsurface, i.e., the number of OH groups on the support surface (silanolgroups in the case of silica) is approximately inversely proportional tothe temperature of drying or dehydration: the higher the temperature thelower the hydroxyl group content. In other words, at each calcinationtemperature the support (e.g., silica) reaches a certain OHconcentration, after which additional heating has no further effect onthe OH concentration.

A slurry of the support material in a non-polar solvent may be preparedby introducing the support material into the solvent, preferably whilestirring, and heating the mixture to about 25 to about 70° C.,preferably to about 40 to about 60° C. The most suitable non-polarsolvents are materials which are liquid at reaction temperatures and inwhich all of the reactants used later during the catalyst preparation,e.g., organomagnesium compounds, oxygen-containing compounds and thelike and transition metal compounds, are at least partially soluble.Preferred non-polar solvents are alkanes, particularly those containingabout 5 to about 10 carbon atoms such as isopentane, hexane, isohexane,n-heptane, isoheptane, octane, nonane, and decane. However, othermaterials including cycloalkanes and aromatic solvents, particularlythose containing about 6 to about 12 carbon atoms such as benzene,toluene, ethylbenzene and the xylenes, may also be used. Of course, itis also possible to use solvent mixtures.

Prior to use, the non-polar solvent should be purified, such as bypercolation through silica gel and/or molecular sieves, to remove tracesof water, molecular oxygen, polar compounds, and other materials capableof adversely affecting catalyst activity. It is to be noted that thetemperature of the slurry before addition of the transition metalcompound for the non-single-site catalyst should not be in excess of 90°C., since otherwise a deactivation of the transition metal component islikely to result. Accordingly, all catalyst synthesis steps arepreferably carried out at a temperature below 90° C., even morepreferred below 80° C.

Following the preparation of a slurry of the support material in anon-polar solvent, the slurry is preferably contacted with anorganomagnesium compound. Preferred organomagnesium compounds for use inthe present invention include dialkylmagnesium compounds of the generalformula (I):R¹ _(m)MgR² _(n)  (I)wherein R¹ and R² are the same or different branched or unbranched alkylgroups containing about 2 to about 12 carbon atoms, preferably about 4to about 10 carbon atoms, and even more preferred about 4 to about 8carbon atoms and m and n are each 0, 1 or 2, provided that the sum (m+n)is equal to the valence of Mg. The most preferred dialkylmagnesiumcompound is dibutylmagnesium. Of course, it is also possible to use morethan one organomagnesium compound, e.g., two different organomagnesiumcompounds.

The purpose of the organomagnesium compound is to increase the activityof the catalyst. For a better understanding of the role of theorganomagnesium compound for the performance of polymerization catalystssuch as those disclosed herein reference may be made to theabove-mentioned article by T. E. Nowlin et al. in J. Polym. Sci.: PartA: Polymer Chemistry, Vol. 29, 1167-1173 (1991). The amount oforganomagnesium compound will generally be greater than about 0.3mmol/g, more preferably greater than about 0.5 mmol/g, even morepreferably greater than 0.7 mmol/g, where the amount of organomagnesiumcompound is given as mmol Mg/g of support material. In the synthesis ofthe catalyst composition for use in the present invention it isdesirable to add not more organo-magnesium compound than will bedeposited—physically or chemically—into the support since any excess ofthe organomagnesium compound in the liquid phase may react with otherchemicals used for the catalyst synthesis and precipitate them outsideof the support. The drying temperature of the support materials affectsthe number of sites on the support available for the dialkylmagnesiumcompound: the higher the drying temperature the lower the number ofsites. Thus, the exact ratio of organomagnesium compound to support willvary and should be determined on a case-by-case basis to assure thatpreferably only so much of the organomagnesium compound is added to theslurry as will be deposited into the support without leaving excessorganomagnesium compound in the liquid phase. Thus the ratios givenbelow are intended only as an approximate guideline and the exact amountof organomagnesium compound is to be controlled by the functionallimitation discussed above, i.e., it should preferably not be greaterthan that which can completely be deposited into the support. Theappropriate amount of the organomagnesium compound can be determined inany conventional manner, e.g., by adding the organomagnesium compound tothe slurry of the support material until free organomagnesium compoundis detected in the liquid phase (e.g., by taking a sample of the liquidphase and analyzing it for Mg by one of several analytical proceduresknown to one of ordinary skill in the art). If organo-magnesium compoundis added in excess of the amount deposited into the support material, itcan be removed, e.g., by filtration and washing of the support material.However, this is less desirable than the embodiment described above.

For example, for the silica support heated at about 600° C., the amountof the organomagnesium compound added to the slurry will generally beless than about 1.7 mmol/g, preferably less than about 1.4 mmol/g, evenmore preferably less than about 1.1 mmol/g.

The treatment of the support material with the organomagnesium compoundcan on principle be carried out at any temperature at which theorganomagnesium compound is stable. The contacting of the slurry of thesupport material in a non-polar solvent with the organomagnesiumcompound will generally be carried out at a temperature between roomtemperature (e.g., 20° C.) and 80° C. Preferably, the addition iscarried out at slightly elevated temperature, e.g., at a temperature ofat least about 30° C., even more preferred at least about 40° C. Afterthe addition of the organomagnesium compound is complete, the slurrywill usually be stirred, preferably at about the temperature ofaddition, for a sufficient time to allow the organomagnesium compound toreact and/or interact with the support material substantiallycompletely. Generally this time will be not less than about 0.1 hours,preferably not less than about 0.5 hours, although stirring for morethan about 2.0 hours will not bring about any significant furtherreaction/interaction.

Next, the support treated with the organomagnesium compound preferablyis contacted with an oxygen-containing organic compound preferablycontaining 1 to about 6 carbon atoms such as, e.g., an aliphatic oraromatic alcohol, an aldehyde, a ketone, an ester, a carbonyl chloride,a carboxylic acid and the like. Preferred, non-limiting examples ofoxygen-containing compounds are monohydric alcohols having 1 to about 6carbon atoms such as, e.g., methanol, ethanol, n-propanol andisopropanol, n-butanol, n-pentanol and n-hexanol. n-Butanol isparticularly preferred.

The amount of oxygen-containing compound employed is preferably suchthat it will react substantially completely with theorganomagnesium/support intermediate material formed after the additionof the organomagnesium compound to the slurried support material.Generally the molar ratio of organomagnesium compound (e.g.,dialkylmagnesium compound) to oxygen-containing compound will be atleast about 1:5, more preferably at least about 1:2, and most preferredat least about 1:1. On the other hand, it is preferred that said ratiois not higher than about 15:1, particularly not higher than about 10:1,with a ratio of not higher than about 6:1, e.g., not higher than 2:1,being even more preferred.

Regarding the temperature at which the oxygen-containing compound isadded to the slurry of support material treated with the organomagnesiumcompound, there are no particular restrictions besides the thermalstability of the materials involved. Generally, the addition will becarried out at a temperature between room temperature and the boilingpoint of the non-polar solvent of the slurry. As a matter of conveniencethe temperature will preferably be about the same as that at which theorganomagnesium compound was added and at which the slurry oforganomagnesium compound-treated support material was stirred before theaddition of the oxygen-containing compound, respectively. Following theaddition of the oxygen-containing compound, the slurry will generally bestirred, preferably at about the temperature of addition, for a timeperiod that is sufficient to allow the oxygen-containing compound tosubstantially completely react/interact with the organomagnesiumcompound-treated support material. Said stirring time is generally atleast about 0.5 hours, preferably at least about 1.0 hour, althoughstirring for more than about 2.0 hours usually does not bring about anysignificant further reaction/interaction.

After the reaction/interaction with the oxygen-containing compound asdescribed above, the resulting slurry of support material is contactedwith one or more (preferably one) transition metal compound for forminga non-single-site polymerization catalyst. During this step, the slurrytemperature is preferably maintained at about 25° C. to about 70° C.,particularly at about 40° C. to about 60° C. As noted above,temperatures in the slurry of about 90° C. or greater are likely toresult in deactivation of the transition metal source. Suitabletransition metal compounds for the non-single-site polymerizationcatalyst include those of elements of Groups IV and V of the PeriodicTable, particularly titanium-containing and vanadium-containingcompounds. Illustrative, non-limiting examples of such compounds aretitanium and vanadium halides, e.g., titanium tetrachloride, vanadiumtetrachloride, vanadium oxytrichloride, titanium and vanadium alkoxides,wherein the alkoxide moiety has a branched or unbranched alkyl radicalof 1 to about 20 carbon atoms, preferably 1 to about 10 carbon atoms,and even more preferably 1 to about 6 carbon atoms (e.g., methoxy,ethoxy, propoxy and isopropoxy). The preferred transition metalcompounds are titanium-containing compounds, particularly tetravalenttitanium-containing compounds. The most preferred titanium compound isTiCl₄.

The amount of transition metal compound(s) for forming thenon-single-site polymerization catalyst is at least in part determinedby the desired ratio of first polymer component to second polymercomponent in the desired ethylene/α-olefin copolymer according to thepresent invention. In other words, because the non-single-sitepolymerization catalyst will produce the first polymer component and thesingle-site polymerization catalyst will produce the second polymercomponent, under otherwise identical polymerization conditions the ratioof first polymer component to second polymer component in the resultingcopolymer will increase with increasing molar ratio of transition metalcompound(s) for forming the non-single-site polymerization catalyst tocompound(s) for forming the single-site polymerization catalyst of thecatalyst combination for use in the present invention. The total amountof catalyst components, on the other hand, is limited by the capabilityof the specific support material employed to accommodate the catalystcomponents. Generally, however, the transition metal compound for thenon-single-site catalyst is employed in an amount that results in anatomic ratio of Mg of the organomagnesium compound (e.g.,dialkylmagnesium compound employed to treat the support) to transitionmetal(s) for the non-single-site catalyst of at least about 0.5:1, morepreferably at least about 1:1, and most preferred at least about 1.7:1.On the other hand it is preferred that said ratio is not higher thanabout 5:1, particularly not higher than about 3:1, a ratio of not higherthan about 2:1 being particularly preferred.

Mixtures of non-single-site polymerization catalyst transition metalcompounds may also be used and generally, no particular restrictions areimposed on the transition metal compounds which may be included. Anytransition metal compound that may be used alone may also be used inconjunction with other suitable transition metal compounds.

After the addition of the transition metal compound(s) for thenon-single-site catalyst is complete, in one embodiment of the catalystsynthesis, the slurry solvent is removed, e.g., by evaporation and/orfiltration, to obtain a preferably free-flowing powder of a catalystintermediate.

Next, incorporation of the metallocene compound(s) (or any othersuitable compound(s)) for forming the single-site polymerizationcatalyst can be undertaken. A metallocene compound usually is activatedwith an aluminoxane which preferably is contacted with the supportmaterial together with the metallocene compound.

Preferred metallocene compounds for use in the present invention havethe general formula (II)Cp_(x)MA_(y)  (II)wherein x is at least 2, M is titanium, zirconium or hafnium, Cprepresents optionally substituted cyclopentadienyl and optionallysubstituted cyclopentadienyl that is part of an aromatic polycyclic ringsystem, provided that at least one Cp is cyclopentadienyl that is partof an aromatic polycyclic ring system, two cyclopentadienyl moieties maybe linked by a bridging group, A is selected from halogen, hydrogen,hydrocarbyl (preferably having 1 to about 12 carbon atoms) andcombinations thereof, and the sum (x+y) is equal to the valence of M.

In the above formula (II), the preferred transition metal atom M iszirconium or hafnium, most preferably zirconium. The substituents on thecyclopentadienyl group or polycyclic ring system, if any, will usuallybe (preferably straight-chain) alkyl groups having 1 to about 6 carbonatoms, such as, e.g., methyl, ethyl, propyl, n-butyl, n-pentyl andn-hexyl. At least one of the cyclopentadienyl moieties is part of an(optionally substituted) polycyclic, e.g., bicyclic or tricyclic,aromatic ring system such as, e.g., indenyl and fluorenyl. At least twoof the cyclopentadienyl moieties may be (and preferably are) bridged,for example, by polymethylene or dialkylsilyl groups, such as —CH₂—,—CH₂—CH₂—, —CR═R@— and —CR═R@-CR═R@- where R═and R@ are lower (e.g.,C₁-C₄) alkyl groups or hydrogen atoms, —Si(CH₃)₂—,—Si(CH₃)₂—CH₂—CH₂—Si(CH₃)₂— and similar bridging groups. If A in theabove formula represents halogen it represents F, Cl, Br and/or I and ispreferably chlorine. If A represents a hydrocarbyl group, it preferablyis an alkyl or aryl group. The alkyl group preferably is astraight-chain or branched alkyl group containing 1 to about 8 carbonatoms, such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl,n-pentyl, n-hexyl and n-octyl.

Of course, as long as the above proviso is satisfied, the Cp moieties inthe above general formula may be the same or different. The same appliesif y is equal to or greater than 2 with respect to the groups A whichmay also be the same or different in that case.

Illustrative, non-limiting examples of metallocene compounds suitablefor making the single-site catalyst for use in the present inventioninclude bis(cyclopentadienyl)metal dihalides, bis(cyclopentadienyl)metalhydridohalides, bis(cyclopentadienyl)metal monoalkyl monohalides andbis(cyclopentadienyl)metal dialkyls wherein the metal is preferablyzirconium or hafnium, the halide groups are preferably chlorine, thealkyl groups (including cycloalkyl groups) preferably have 1 to about 6carbon atoms and at least one of the cyclopentadienyl moieties is fusedwith a benzene ring to afford, e.g., an indenyl or fluorenyl ringsystem. Preferably, the cyclopentadienyl moieties are connected by abridging group. Illustrative, non-limiting examples of correspondingmetallocenes include ethylenebis(indenyl)zirconium dichloride,ethylenebis(indenyl)-zirconium dibromide,ethylenebis(indenyl)dimethylzirconium,ethylenebis(indenyl)-diphenylzirconium,ethylene-bis(indenyl)methylzirconium chloride, isopropylideneethylene(cyclopentadienyl)-(fluorenyl)zirconium dichloride,isopropylidene(cyclopentadienyl)(methylcyclopentadienyl)-zirconiumdichloride, dimethylsilylbis(indenyl)zirconium dichloride,dimethylsilyl(cyclo-pentadienyl)(fluorenyl)zirconium dichloride,diphenylsilylbis(indenyl)zirconium dichloride andmethylphenylsilylbis(indenyl)zirconium dichloride, as well asderivatives of these metallocenes wherein thecyclopentadienyl-containing moieties have up to three methylsubstituents. Of these, ethylenebis(indenyl)zirconium dichloride anddimethylsilyl(cyclopentadienyl)(fluorenyl)zirconium dichloride arepreferred metallocene compounds for use in the present invention.

Of course, mixtures of compounds for forming the single-sitepolymerization catalyst such as mixtures of metallocene compounds mayalso be used. Any compound that may be used alone may also be used inconjunction with other suitable compounds. Moreover, the amount ofmetallocene or any other single-site polymerization catalyst compound(s)is such that it results in the desired ratio of first component tosecond component in the copolymer, which ratio in turn is at least inpart determined by the atomic ratio of metal(s) of the non-single-sitepolymerization catalyst transition metal compound(s) to metal(s) of thesingle-site polymerization catalyst compound(s). Generally said atomicratio is at least about 1:1, more preferably at least about 2:1 or atleast about 3:1, and most preferred at least about 4:1. On the otherhand, said ratio is generally not higher than about 30:1, preferably nothigher than about 15:1, with a ratio of not higher than about 10:1 beingparticularly preferred.

Incorporation of a metallocene compound into the carrier can beaccomplished in various ways, usually together with an aluminoxane.Incorporation of either or both the aluminoxane and the metallocenecompound can be into a slurry of catalyst intermediate in a non-polarsolvent. The aluminoxane and metallocene compound can be added in anyorder, or together (e.g., as solution in an aromatic or the samenon-polar solvent), to that slurry or to the isolated catalystintermediate. A preferred way of combining aluminoxane and metalloceneis to add a solution of these two components in an aromatic solvent(preferably toluene) to a slurry of the catalyst intermediate in adifferent non-polar solvent. This is preferably done at roomtemperature, but higher temperatures can also be used as long as thestability of the various materials present is not affected thereby.Following the addition, the resulting mixture is usually stirred(preferably at room temperature) for sufficient time to allow all of thecomponents to react and/or interact substantially completely with eachother. Generally the resulting mixture is stirred for at least about 0.5hours, preferably at least about 1.0 hours, while stirring times inexcess of about 10 hours usually do not offer any particular advantage.Thereafter the liquid phase can be evaporated from the slurry to isolatea free-flowing powder containing both non-single-site polymerizationcatalyst compound and metallocene single-site polymerization catalystcompound. Filtering is usually avoided to substantially eliminate theloss of catalytic components. If evaporation of the liquid phase underatmospheric pressure would require temperatures that might adverselyaffect the catalyst components (degradation) reduced pressure may beused

As mentioned above, preferably the intermediate comprising thenon-single-site polymerization catalyst transition metal is firstrecovered from the slurry in the initially employed non-polar solvent orsolvent mixture (e.g., by filtration and/or distilling the solvent) andis then reslurried in the same or a different non-polar solvent.Non-limiting examples of suitable non-polar solvents for the abovepurpose (i.e., reslurrying of intermediate) include, but are not limitedto, aliphatic, cycloaliphatic and aromatic hydrocarbons such as thoseset forth above for use in the preparation of the initial slurry of thesupport material in a non-polar solvent, e.g., n-pentane, isopentane,n-hexane, methylcyclopentane, isohexanes, cyclohexane, n-heptane,methylcyclohexane, isoheptanes, benzene, toluene, ethylbenzene, xylenesand mixtures of two or more thereof.

The aluminoxanes preferably employed in combination with metallocenetransition metal compounds are not particularly limited. They includeoligomeric linear and/or cyclic alkylaluminoxanes of the general formulaR—(Al(R)—O)_(n)—AlR₂ for oligomeric, linear aluminoxanes and(—Al(R)—O—)_(m) for oligomeric cyclic aluminoxanes wherein n is 1-40,preferably 10-20, m is 3-40, preferably 3-20, and R is a C₁-C₈ alkylgroup, and preferably methyl to provide methylaluminoxane (MAO). MAO isa mixture of oligomers with a very wide distribution of molecularweights and usually with an average molecular weight of about 1200. MAOis typically kept in solution in toluene. It is also possible to use,for the present purpose, aluminoxanes of the type just described whereinthe alkyl groups in the above general formulae are different. Apreferred example thereof is modified methylaluminoxane (MMAO) whereinin comparison to MAO a part of the methyl groups is replaced by otheralkyl groups. Modified methylaluminoxanes are disclosed, e.g., in U.S.Pat. No. 6,001,766, the disclosure of which is expressly incorporated byreference herein in its entirety.

The aluminoxane or mixture of aluminoxanes usually is employed in anamount which results in sufficient activation of the metallocenetransition metal compound-derived catalyst component of the catalystcombination for use in the present invention. Because the metallocenetransition metal compound-derived catalyst produces the second componentof the copolymer to be made therewith, under otherwise identicalpolymerization conditions the weight fraction of second polymercomponent usually increases with increasing amount of aluminoxaneemployed. Generally, the atomic ratio of Al in the aluminoxane to metalin the metallocene compound(s) is at least about 10:1, more preferablyat least about 50:1, and most preferred at least about 80:1. On theother hand said ratio is generally not higher than about 1,000:1,particularly not higher than about 500:1, with a ratio of not higherthan about 300:1 being particularly preferred.

An alternative way of incorporation of the aluminoxane or the activatedmetallocene compound-derived catalyst (metallocene-aluminoxane) onto thesupport is by stripping the intermediate of the solvent to form afree-flowing powder. This free-flowing powder can then be impregnated bydetermining the pore volume of the intermediate material and providingan aluminoxane (or metallocene-aluminoxane) solution in a volume equalto or less than two times the total pore volume of the intermediatematerial, whereafter the dry non-single-site/metallocene catalystcombination is recovered. A more detailed description of saidimpregnation (incorporation) procedure can be found in, e.g., U.S. Pat.No. 5,614,456, the disclosure whereof is incorporated herein byreference in its entirety.

Generally, it is preferred to use the catalyst combination for use inthe present invention in combination with a cocatalyst (that primarilyactivates the non-single-site polymerization catalyst). Suitablecocatalysts are organometallic compounds of Group IA, IB, IIA, IIB, IIIAor 111B elements, such as, e.g., aluminum, sodium, lithium, zinc, boronand magnesium, and in general any one or a combination of any of thematerials commonly employed to activate Ziegler-Natta olefinpolymerization catalyst components. Examples thereof are alkyls,hydrides, alkylhydrides and alkylhalides of the mentioned elements, suchas n-butyllithium, diethylzinc, di-n-propylzinc and triethylboron.Usually, however, the cocatalyst will be an alkylaluminum compound,preferably a compound of the general formula (III):R⁵ _(a)AlX_(b)  (III)

-   -   wherein a is 1, 2 or 3, R⁵ is a linear or branched alkyl group        containing 1 to about 10 carbon atoms, X represents hydrogen        atom or halogen atom and b is 0, 1 or 2, provided that the sum        (a+b) is 3.

Preferred types of compounds of the general formula (III) above aretrialkylaluminum, dialkylaluminum hydride, dialkylaluminum halide,alkylaluminum dihydride and alkylaluminum dihalide. The halidepreferably is Cl and/or Br. Preferred alkyl groups are linear orbranched and contain 1 to about 6 carbon atoms, such as methyl, ethyl,propyl, isopropyl, butyl, isobutyl, straight-chain and branched pentyland hexyl groups. Specific examples of suitable cocatalysts aretrimethylaluminum, triethylaluminum, tripropylaluminum,triisopropylaluminum, tributylaluminum, triisobutylaluminum,trihexylaluminum, trioctylaluminum, diisobutylhexylaluminum,isobutyldihexylaluminum, diisobutylaluminum hydride, dihexylaluminumhydride, diethylaluminum chloride, and diisobutylaluminum chloride. Apreferred cocatalyst is trimethylaluminum (TMA). Other alkylaluminumcompounds, for example those wherein X in the above formula (III) isalkoxy (e.g. having 1 to 6 carbon atoms) may also be employed.

The amount of cocatalyst is sufficient to (further) activate thenon-single-site polymerization catalyst of the catalyst combination foruse in the present invention. A suitable amount can be determined by oneof ordinary skill in the art. If too little cocatalyst is used, thecatalyst may not be completely activated, leading to wastednon-single-site polymerization catalyst transition metal compound andalso failing to provide the target ratio of first polymer component tosecond polymer component in the ethylene copolymer to be produced. Toomuch cocatalyst, on the other hand, results in wasted cocatalyst, andmay even give rise to unacceptable impurity of the copolymer produced.Generally, however the amount of cocatalyst employed is based on theamount of ethylene fed to the polymerization process. The amount ofcocatalyst generally is at least about 5 ppm, more preferably at leastabout 20 ppm, and most preferred at least about 40 ppm. On the otherhand, the amount of cocatalyst generally is not higher than about 500ppm, preferably not higher than about 400 ppm and particularly nothigher than about 300 ppm (based on the ethylene employed).

Polymerization

A catalyst combination prepared as described above may be used topolymerize ethylene in conjunction with one or more α-olefins to providethe copolymers according to the present invention. Illustrative,non-limiting examples of α-olefins that may be used are those having 3to about 10 carbon atoms, e.g., propylene, 1-butene, 1-pentene,1-hexene, 4-methyl-1-pentene, 1-heptene and 1-octene, preferably1-butene, 1-pentene, 1-hexene or 4-methyl-1-pentene and, mostpreferably, 1-hexene. The polymerization may be carried out using anysuitable, conventional olefin polymerization process, such as slurry,solution or gas phase polymerization, but preferably it is carried outin a slurry reactor or in a gas phase reactor, particularly afluidized-bed reactor. The polymerization can be carried out batchwise,semicontinuously or continuously. Preferably, the reaction is conductedin the substantial absence of catalyst poisons, such as moisture, carbonmonoxide and acetylene, with a catalytically effective amount of thecatalyst combination at temperature and pressure conditions sufficientto initiate the polymerization reaction. Particularly desirable methodsfor producing the copolymers of the present invention are in a slurry orfluidized bed reactor. Such reactors and means for operating it aredescribed by, e.g., U.S. Pat. Nos. 4,001,382, 4,302,566, and 4,481,301,the entire contents of which are expressly incorporated herein byreference. The polymer produced in such reactors contains (deactivated)catalyst particles because the catalyst is not separated from thepolymer.

The molecular weight of the copolymer as a whole may suitably becontrolled in a manner well known to those skilled in the art, e.g., byadding small amounts of water to the polymerization reactor. Moreover,hydrogen may be added as chain transfer agent. The amount of hydrogenwill generally be between about 0 to about 2.0 moles of hydrogen permole of ethylene employed.

Polymerization temperature and time can be determined by one of ordinaryskill in the art based on a number of factors, such as, the type ofpolymerization process to be used. As chemical reactions generallyproceed at a greater rate with higher temperature, polymerizationtemperature should be high enough to obtain an acceptable polymerizationrate. In general, therefore, polymerization temperatures are higher thanabout 30° C., more often higher than about 75° C. On the other hand,polymerization temperature should not be so high as to causedeterioration of, e.g., catalyst or copolymer. Specifically, withrespect to a fluidized-bed process, the reaction temperature ispreferably not so high as to lead to sintering of copolymer particles.In general, polymerization temperatures are below about 115° C., morepreferably below about 105° C.

The polymerization temperature used in the process is in part determinedby the density of the copolymer to be produced. More in particular, themelting point of the copolymer depends on the copolymer density. Thehigher the density of the copolymer, the higher its melting point.Therefore, lower density copolymers are produced at lower temperaturesto avoid melting or sintering of the copolymer particles being producedin the reactor. Thus, without limiting the present invention, copolymershaving densities below about 0.92 g/cm³ are polymerized at a temperaturepreferably above about 60° C., but preferably below about 90° C.Copolymers having densities of about 0.92 to about 0.94 g/cm³ arepolymerized at a temperature preferably above about 70° C., butpreferably below about 100° C. When a fluidized-bed reactor is used, theperson of ordinary skill in the art is readily able to determineappropriate pressures to use. Fluidized-bed reactors can be operated atpressures of up to about 1000 psi or more, and are generally operated atpressures below about 350 psi. Preferably, fluidized-bed reactors areoperated at pressures above about 150 psi. As is known in the art,operation at higher pressures favors heat transfer because an increasein pressure increases the unit volume heat capacity of the gas.

Once a catalyst is activated, the activated catalyst has a limitedlifetime before it becomes deactivated. As is known to those of ordinaryskill in the art, the half-life of an activated catalyst depends on anumber of factors, such as the species of catalyst (and cocatalyst), thepresence of impurities (e.g., water and oxygen) in the reaction vessel,and other factors. An appropriate length of time for carrying out apolymerization can be determined by the person skilled in the art foreach particular situation.

The copolymers of the present invention contain about 5 to about 20percent by weight of units derived from α-olefin. For example, thecopolymer may contain at least about 5.5, at least about 6, at leastabout 7, at least about 10, at least about 12, or even at least about 15percent by weight of units derived from at least one α-olefin. Anexemplary upper limit is about 18 percent by weight.

The copolymers of the present invention are characterized by showing (a)at least two CRYSTAF peak temperatures which differ by at least about15° C., preferably at least about 20° C., even more preferably at leastabout 25° C., for example by about 30° C. or even higher, and/or (b) atleast two DSC melting peak temperatures which differ by at least about15° C., preferably at least about 20° C., for example by about 25° C. oreven higher. Preferred copolymers of the present invention show theminimum differences indicated above in both the CRYSTAF and the DSCmelting peak temperatures. Also, in the preferred copolymers of thepresent invention at least one CRYSTAF peak appears in the temperaturerange of from about 75° C. to about 95° C. Additionally oralternatively, at least one DSC melting peak temperature is in the rangeof from about 115° C. to about 135° C. The procedures to be used for thedetermination of the CRYSTAF peak and DSC melting peak temperatures of acopolymer sample are described in detail in the experimental sectionbelow.

The differences in the at least two CRYSTAF peaks and the at least twoDSC melting peak temperatures, respectively, are an indication that thecomonomer α-olefin) contents in the first component produced by thenon-single-site polymerization catalyst and the second componentproduced by the single-site polymerization catalyst differsignificantly. In particular, the comonomer incorporation rate of thesingle-site polymerization catalyst is higher than the comonomerincorporation rate of the non-single-site polymerization catalyst. Thisdifference has a pronounced effect on the properties of thecorresponding copolymer only because at the same time, the comonomercontent of the entire copolymer is high, i.e., at least about 5 weightpercent and up to about 20 weight percent. Only this high comonomercontent of the copolymer of the present invention can bring about asignificant absolute difference in comonomer content of the individualcomponents thereof, i.e., the component produced by the non-single-sitepolymerization catalyst (e.g., Ziegler catalyst) and the componentproduced by the single-site polymerization catalyst (e.g.,metallocene-based catalyst). This difference translates intosignificantly different properties of the individual copolymercomponents, the more so since single-site polymerization catalystsusually incorporate α-olefin comonomer in a much more uniform mannerinto the copolymer molecule than non-single-site polymerizationcatalysts such as conventional Ziegler-Natta catalysts, which resultsin, e.g., a different crystallization behavior (for example, a Zieglercatalyzed copolymer component may be expected to have a highercrystallization tendency than a metallocene catalyzed copolymercomponent).

Copolymers of the present invention which have an essentially unimodalmolecular weight distribution, i.e., wherein the average molecularweights of the individual components thereof are similar so as to resultin a quasi-unimodal instead of a bimodal molecular weight distributionof the copolymer (as evidenced by, e.g., a single peak in the gelpermeation chromatogram, as opposed to two distinct (distinguishable)peaks in the case of a “true” bimodal distribution, see e.g., FIG. 4)are particularly preferred. An advantage of the catalyst combinationspreferably used according to the present invention is that thesingle-site catalyst produces a comparatively high molecular weightcopolymer component at a given molar ratio of ethylene and hydrogen orproduces a copolymer component having a molecular weight which is closeto that of the copolymer component produced by the non-single-sitepolymerization catalyst, respectively.

The density of copolymers of the present invention is to a large partdetermined by the amount of α-olefin comonomer(s) in the copolymermolecule. In order to achieve the CRYSTAF and DSC melting peaktemperature differences discussed above, enough α-olefin comonomer is tobe copolymerized with ethylene to achieve a level of at least about 5weight percent of the α-olefin comonomer(s) in the copolymer. The amountof comonomer needed to achieve a predetermined density depends, interalia, on the particular α-olefin(s) being employed. Further, the variouscontemplated α-olefins have different reactivity rates, relative to thereactivity rate of ethylene, with respect to the copolymerizationthereof with the polymerization catalysts. Therefore, the amount of aspecific α-olefin to be fed to the reactor in order to achieve apredetermined comonomer concentration in the copolymer will also dependon the reactivity of that α-olefin.

According to the present invention it is preferred to polymerizeethylene and at least one α-olefin, particularly 1-hexene, to obtaincopolymers having a density of not higher than about 0.93 g/cm³, morepreferably not higher than about 0.925 g/cm³, e.g., not higher thanabout 0.92 g/cm³. While there is no particular lower density limit, thedensity of the copolymer of the present invention will usually not belower than about 0.89 g/cm³, preferably not lower than about 0.90 g/cm³.Of course, other ethylenically unsaturated comonomers may also bepresent in the copolymers of the invention (resulting in terpolymers,tetrapolymers, etc.), but preferably in amounts not higher than about 2weight %, more preferably not higher than about 1 weight %.

The melt index (MI) of the present copolymers is preferably at leastabout 0.1 g/10 min, more preferred at least about 0.2 g/10 min, butpreferably not higher than about 100 g/10 min, and particularly nothigher than about 50 g/10 min. The melt flow ratio (MFR, flow index/meltindex, as determined according to ASTM D1238 at 190° C. at a load of21.6 and 2.16 kg, respectively) of the copolymers of the presentinvention preferably is at least about 17, more preferably at leastabout 20, but preferably not higher than about 100, more preferably nothigher than about 70, e.g., not higher than about 60.

Additionally, the molecular weight distribution of the copolymers of thepresent invention, expressed as M_(w)/M_(n) (weight average molecularweight/number average molecular weight, as determined by gel permeationchromatography, see experimental section below for details) preferablyis at least about 2.5, more preferably at least about 3.0, butpreferably not higher than about 10, more preferably not higher thanabout 9, e.g., not higher than about 7. The copolymers of the presentinvention are particularly suitable for the manufacture of film, e.g.,blown film. Other articles for the manufacture whereof the copolymers ofthe present invention may advantageously be used include extrudedarticles such as sheets as well as molded articles such as articles madeby injection molding or blow molding.

In general, the ethylene/α-olefin copolymers of the present inventionare preferably extruded or blown into films. For example, films can beproduced which are about 0.2 to 10 mils, preferably about 0.5 to 5 milsin thickness.

The present copolymers may be combined with various additivesconventionally added to polymer compositions, such as lubricants,fillers, stabilizers, antioxidants, compatibilizers, pigments, etc. Manyadditives can be used to stabilize the products. For example, additivepackages comprising hindered phenol(s), phosphites, antistats andstearates, for addition to resin powders, can be used for pelletization.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described in the detailed descriptionwhich follows, in reference to the noted plurality of drawings by way ofnon-limiting examples of exemplary embodiments of the present invention.In the drawings:

FIG. 1 shows a DSC (differential scanning calorimetry) curve of thecopolymer produced in Polymerization Example 1;

FIG. 2 shows the melting points of ethylene/1-hexene copolymers producedby Ti Ziegler catalysts on the one hand and zirconocene catalysts on theother hand as a function of the 1-hexene concentration;

FIG. 3 shows a DSC curve of the copolymer produced in PolymerizationExample 2;

FIG. 4 shows a GPC curve of the copolymer produced in PolymerizationExample 2;

FIG. 5 shows a CRYSTAF curve of the blended copolymers produced inPolymerization Examples 3 and 4;

FIG. 6 shows a CRYSTAF curve of the copolymer produced in PolymerizationExample 2;

FIG. 7 shows a CRYSTAF curve of an ethylene/1-hexene copolymer producedby a conventional Ziegler (non-single-site) polymerization catalyst; and

FIG. 8 shows the 1% flexural modulus as a function of density forethylene/1-hexene copolymers in accordance with the present inventionand produced by conventional Ziegler catalysts, respectively.

The following Examples further illustrate the essential features of thepresent invention. However, it will be apparent to those skilled in theart that the specific reactants and reaction conditions used in theExamples do not limit the scope of the present invention.

The properties of the polymers produced in the Examples were determinedas follows:

Analysis of the Resin Produced

Prior to testing the polymers are processed as described below.Additives—1000 ppm each of Irganox™ 1010 (hindered phenol antioxidant)and Irgafos' 168 (phosphite antioxidant), both produced by CK WitcoCorp., and 500 ppm AS900 (antistatic agent manufactured by Ciba-Geigy,Switzerland), are dry blended with the granular resin. The mixture isthen melt mixed using either a Brabender twin screw compounder (¾″ screwdiameter) at melt temperatures of less than 200° C., with a nitrogenpurge to the feed throat, or a 40 gram Brabender batch mixer.

The Flow Index (FI), g/10 min, at 190° C. was determined as specified inASTM D 1238 using a load of 21.6 kg.

The Melt Index (MI), g/10 min, at 190° C. was determined as specified inASTM D 1238 using a load of 2.16 kg.

The density (g/cm³) was determined as specified in ASTM D 1505-68 withthe exception that the density measurement is taken 4 hours instead of24 hours after the sample is placed in the density column.

Tensile strength values (tensile yield, ultimate tensile strength,elongation at break and elongation at yield) were measured (machinedirection (“MD”) and transverse direction (“TD”)) in accordance withASTM D882-97. The film gauge was measured using ASTM D5947-96 Method C.

1% Secant (both MD and TD) was determined in accordance with ASTMD882-97.1% Flex was determined according to ASTM D-790A.

Elmendorf tear was determined in accordance with ASTM D1922-94a.

Dart Impact Strength (sometimes termed “dart drop”) was measured inaccordance with ASTM D1709 Method A, at 26 inches (66 cm).

Gloss was measured according to ASTM D-2457.

Haze was measured according to ASTM D-1003.

CRYSTAF Peak Temperature Determination

The CRYSTAF Peak Temperature Determination is conducted using a CRYSTAFinstrument available from PolymerChar (Valencia, Spain). The copolymersample is dissolved at 150° C. in trichorobenzene to a concentration of0.1 weight percent. The copolymer is dissolved at this temperature for45 minutes. The solution is then kept at 100° C. for 30 minutes,whereafter it is cooled to 30° C. at a rate of 0.2° C./min. At regularintervals during cooling an infrared detector measures the concentrationof polymer in solution. A curve of polymer concentration as function oftemperature is obtained. The derivative of this curve is the thecomonomer distribution. Highly branched species correspond to a lowtemperature peak while less branched species are represented by a hightemperature peak. The copolymers of the present invention, prepared asdescribed below, display (at least) two distinct peaks, indicating abimodal comonomer distribution.

DSC Melting Curves

The samples are first heated to 150° C. and then cooled at a rate of0.5° C./min. Thereafter, the melting endotherm is generated by heatingthe samples from 40-140° C. at a rate of 2° C./min, thereby determiningthe peak melting temperature. Highly branched (more comonomer) copolymerspecies will melt at a low peak temperature while unbranched (nocomonomer) polymer species will melt at high temperature. The presentcopolymers typically will display two peaks, suggesting a bimodalcomonomer distribution. FIGS. 1 and 3 illustrate melting endotherms asmeasured by DSC.

Comonomer Content

Comonomer content is measured by an infrared spectroscopic methoddescribed in T. E. Nowlin, Y. V. Kissin and K. P. Wagner, “High ActivityZiegler-Natta Catalyst for the Preparation of Ethylene Copolymers”,Journal of Polymer Science: Part A; Polymer Chemistry, vol. 26, pages755-764 (1988), the disclosure whereof is expressly incorporated hereinby reference in its entirety.

Molecular Weight Distribution

The molecular weight distribution is determined by a standard GelPermeation Chromatography (GPC) technique using a Waters 150 C hightemperature GPC. The polymer solution is prepared in trichlorobenzene ata concentration of 0.1 percent. Four high temperature columns with poresizes of 1E3, 1E4 and 2×1E6 are used. Narrow MWD polystyrene calibrationstandards are used to generate a calibration curve which is converted toequivalent polyethylene molecular weights using the universalcalibration curve and Mark Houwink constants.

EXPERIMENTS Catalyst Preparation Example 1

(a) Under an inert atmosphere, 8.018 g of Davison grade 955 silica wasplaced into a 300 ml pear flask containing a magnetic stirring bar. Thesilica was previously calcined for 12 hours at 600° C. under drynitrogen. The flask was then placed into a silicone oil bath set at 55°C. and then 100-150 ml of dry heptane was added to the flask. Thecontents of the flask were stirred and 7.0 ml of a 0.829 Molar solutionof dibutylmagnesium (DBM) in heptane was added to the flask using asyringe and stirring was continued for two hours. Next, 4.40 ml of a1.254 Molar solution of 1-butanol in heptane was added to the flask andstirring continued for 2 h, all at about 55° C. Then, 3.60 ml of a 0.959Molar solution of TiCl₄ in heptane was added to the flask and stirringcontinued for 2h. Finally, the solvents were removed with a nitrogenpurge for two hours to yield 9.236 g of a light tan free-flowing powder.Ti found: 1.69 wt %; Mg found 1.49 wt %.

(b) Under an inert atmosphere, 0.082 g ofrac-ethylenebis(indenyl)zirconium dichloride was added to a 10 ml serumbottle, followed by 5.0 ml (4.795 g) of a toluene solution ofmethylalumoxane containing 13.4 wt % Al. The contents of the serumbottle were shaken vigorously to afford Solution A.

(c) Under an inert atmosphere, 2.68 g of the powder of (a) above wasadded to a 200 ml flask containing a magnetic stirring bar andapproximately 25 ml of dry heptane was added to the flask. Whilestirring the contents of the flask at room temperature, 2.4 ml ofSolution A (see (b) above) was added dropwise to the flask. The contentsof the flask were stirred for one hour, then the flask was placed intoan oil bath at 40° C. and solvents were removed with a nitrogen purgefor about two hours. After this time, 3.23 g of a free-flowing powderwas obtained.

Catalyst Preparation Example 2

(a) Under an inert atmosphere, 0.086 g of dimethylsily(cyclopentadienyl)(9-fluorenyl)zirconium dichloride was added to a 10 ml serum bottlefollowed by 5.0 ml (4.738 g) of a toluene solution of methylalumoxanecontaining 13.4 wt % Al. The contents of the serum bottle were shakenvigorously to afford Solution B.

(b) Under an inert atmosphere, 2.59 g of the powder described inCatalyst Preparation Example 1 (a) was added to a 200 ml flaskcontaining a magnetic stirring bar, and approximately 25 ml of dryheptane was added to the flask. While stirring the contents of the flaskat room temperature, 4.0 ml of Solution B (see (a) above) was addeddropwise to the flask. The contents of the flask were stirred for 1.5hours, then the flask was placed into an oil bath at 40° C. and solventswere removed with a nitrogen purge for about two hours. After this time,3.60 g of a free-flowing powder was obtained.

Polymerization Example 1

An ethylene/1-hexene copolymer was prepared with the catalyst ofCatalyst Preparation Example 1. A 1.6 liter stainless steel autoclave,equipped with a turbine stirrer, and under a slow nitrogen purge at 46°C. was filled with 500 ml of dry heptane and 200 ml of 1-hexene,followed by 1.1 ml of a 2.0 Molar solution of trimethylaluminum inheptane. The reactor was closed and the stirring speed was set at 900rpm the internal temperature was increased to 95° C., and the internalpressure was increased from 10 psi to 23 psi by the addition ofhydrogen. Then, ethylene was introduced to the reactor and the internalpressure was increased to 210 psi. Finally, 0.0336 g of the catalystprepared in Catalyst Preparation Example 1 was added to the autoclave.The reactor pressure was maintained at 210 psi for 30 minutes afterwhich the ethylene flow to the reactor was stopped and the reactor wascooled to room temperature. The contents of the autoclave were removedand all solvents were evaporated to yield 102.3 g of copolymer.

Polymerization Example 2

An ethylene/1-hexene copolymer was prepared with the catalyst ofCatalyst Preparation Example 2. A 1.6 liter stainless steel autoclave,equipped with a turbine stirrer, and under a slow nitrogen purge at 46°C. was filled with 750 ml of dry heptane and 120 ml of 1-hexene,followed by 1.1 ml of a 2.0 Molar solution of trimethylaluminum inheptane. The reactor was closed and the stirring speed was set at 900rpm, the internal temperature was increased to 85° C., and the internalpressure was increased from 6 psi to 26 psi by the addition of hydrogen.Then, ethylene was introduced to the reactor and the internal pressurewas increased to 210 psi. Finally, 0.0301 g of the catalyst prepared inCatalyst Preparation Example 2 was added to the autoclave. The reactorpressure was maintained at 202 psi for 60 minutes after which theethylene flow to the reactor was stopped and the reactor was cooled toroom temperature. The contents of the autoclave were removed and allsolvents were evaporated to yield 62.2 g of copolymer.

The data collected from the copolymers of Polymerization Examples 1 and2 is summarized below in Table I. TABLE I Polym. MI FI MFR 1-HexeneDensity Ex. No. g/10 min g/10 min (FI/MI) mol % (*) g/cm³ 1 4.2 169 404.05 0.916 2 1.1 29.2 27 2.40 n.d.(*) mol % 1-hexene in the total polymer samplen.d. = not determined

The DSC data on the copolymer prepared in Polymerization Example 1showed two melting points (FIG. 1), one peak at 95.08° C. and a secondpeak at 127.12° C. The melting point as a function of the amount of1-hexene in the copolymer is shown in FIG. 2 for polymer produced by thezirconium and the titanium active centers, respectively. Based on themelting points determined by DSC as shown in FIG. 1 and the calibrationcurves of FIG. 2, it can be calculated that the copolymer produced inPolymerization Example 1 is an in situ blend of copolymer provided bythe zirconium active site which contains about 7.0 mol % units derivedfrom 1-hexene and the copolymer provided by the titanium active sitewhich contains about 2.7 mol % units derived from 1-hexene. Therefore,approximately 70% and 30% of the total copolymer was produced by thetitanium and zirconium active centers, respectively.

The DSC data on the polymer prepared in Polymerization Example 2 showedtwo melting points (FIG. 3), one peak at 101.8° C. and a second peak at128.91° C. Hence, the polymer produced in Polymerization Example 2 is anin situ blend of copolymer provided by the zirconium active site whichcontains about 5.5 mol % units derived from 1-hexene and the copolymerprovided by the titanium active site which contains about 1.5 mol %units derived from 1-hexene. Therefore, approximately 78% and 22% of thecopolymer prepared in Polymerization Example 2 was produced by thetitanium and zirconium active centers, respectively. The GPC of thecopolymer of Polymerization Example 2 indicates a unimodal molecularweight distribution (FIG. 4), suggesting that the two catalysts producedpolymers with similar average molecular weights.

Catalyst Preparation Example 3

(a) 6.673 g of Davison Grade 955 silica previously calcined at 600° C.for 4 hours was added to a 300 ml flask containing a magnetic stir bar.Next, about 100 ml of dry heptane was added to the flask, and the flaskwas placed into an oil bath at 55° C. Dibutylmagnesium (6.0 ml of a0.801 Molar solution in heptane) was added to the flask and the contentswere stirred for 60 minutes. Next, 3.64 ml of 1-butanol (1.254 Molarsolution in heptane) was added to the flask and stirring continued for60 minutes. Finally, 3.0 ml of a 0.959 Molar solution of titaniumtetrachloride in heptane was added to the flask, all at about 55° C.After 60 minutes all solvents were removed under a nitrogen purge toyield 7.58 g of a dry powder. Ti (found) 1.79 wt %.

(b) 0.086 g of dimethylsilyl(cyclopentadienyl)(9-fluorenyl)zirconiumdichloride was added to a 10 ml serum bottom followed by 4.738 grams ofa methylalumoxane/toluene solution containing 13.4 wt % aluminum,affording Solution C.

(c) 2.59 g of the titanium catalyst component of step (a) above wereplaced into a 200 ml flask containing a magnetic stir bar and about 35ml of heptane. At room temperature and with very good mixing, 4.0 ml ofSolution C of (b) above was added dropwise to the flask. Stirring wascontinued for 1.5 hours and then the flask was placed into an oil bathat 40° C. and solvents were removed under a nitrogen purge to yield 3.60g of a purple powder. Analytical results: Al, 12.8 wt %, Mg, 0.93 wt %,Ti 1.11 wt %, Zr, 0.32 wt %.

Polymerization Example 3

A 1.6 liter stainless autoclave under a slow nitrogen purge at 41° C.was filled with 750 ml of dry heptane and 200 ml of dry 1-hexene,followed by the addition of 1.1 ml of a 2.0 Molar solution oftrimethylaluminum in hexane. The reactor was closed and stirring speedwas set at 900 rpm, the internal temperature was increased to 83° C.,and the internal pressure was increased from 6 psig to 23 psig with theaddition of hydrogen. Ethylene was introduced to maintain an internalpressure of 210 psig and then 0.0271 g of the catalyst prepared inCatalyst Preparation Example 3 was injected into the reactor. Theinternal temperature was maintained at 85° C. for one hour and then theethylene flow to the reactor was stopped and the reactor cooled to roomtemperature. 54.8 g of copolymer was isolated from the reactor. Thecopolymer contained 3.4 mol % units derived from 1-hexene and exhibiteda Flow Index of 33.3 g/10 min and a Melt Index of 1.04 g/10 min.

Polymerization Example 4

A 1.6 liter stainless steel autoclave under a slow nitrogen purge at 36°C. was filled with 750 ml of dry heptane and 200 ml of dry 1-hexene,followed by the addition of 1.1 ml of a 2.0 Molar solution oftrimethylaluminum in hexane. The reactor was closed and the stirringspeed was set at 900 rpm, the internal temperature was increased to 84°C., and the internal pressure was increased from 6 psig to 26 psig withthe addition of hydrogen. Ethylene was introduced to maintain aninternal pressure of 210 psig and then 0.0285 g of the catalyst preparedin Catalyst Preparation Example 3 was injected into the reactor. Theinternal temperature was maintained at 85° C. for one hour and then theethylene flow to the reactor was stopped and the reactor cooled to roomtemperature. 61.1 g of copolymer was isolated from the reactor. Thecopolymer contained very similar resin characteristics compared to thatof Polymerization Example 3.

The copolymers produced in Polymerization Examples 3 and 4 were combinedinto one product sample.

Polymerization Example 5

A 1.6 liter stainless steel autoclave under a slow nitrogen purge at 45°C. was filled with 750 ml of dry heptane and 200 ml of dry 1-hexene,followed by the addition of 1.1 ml of a 2.0 Molar solution oftrimethylaluminum in hexane. The reactor was closed and the stirringspeed was set at 900 rpm, the internal temperature was increased to 85°C., and the internal pressure was increased from 6 psig to 22 psig withthe addition of hydrogen. Ethylene was introduced to maintain aninternal pressure of 210 psig and then 0.0301 g of the catalyst ofCatalyst Preparation Example 3 was injected into the reactor. Theinternal temperature was maintained at 85° C. for one hour and then theethylene flow to the reactor was stopped and the reactor cooled to roomtemperature. 70.5 g of copolymer was isolated from the reactor. Thecopolymer contained 3.4 mol % units derived from 1-hexene and exhibiteda Flow Index of 14.0 g/10 min and a Melt Index of 0.48 g/10 min.

Polymerization Example 6

A 1.6 liter steel autoclave under a slow nitrogen purge at 46° C. wasfilled with 750 ml of dry heptane and 200 ml of dry 1-hexene, followedby the addition of 1.1 ml of a 2.0 Molar solution of trimethylaluminumin hexane. The reactor was closed and the stirring speed was set at 900rpm, the internal temperature was increased to 85° C., and the internalpressure was increased from 7 psig to 22 psig with the addition ofhydrogen. Ethylene was introduced to maintain an internal pressure of210 psig and then 0.0276 grams of the catalyst of Catalyst PreparationExample 3 was injected into the reactor. The internal temperature wasmaintained at 85° C. for one hour and then the ethylene flow to thereactor was stopped and the reactor cooled to room temperature. 50.9grams of copolymer was isolated from the reactor. The copolymercontained 3.0 mol % 1-hexene and exhibited a Flow Index of 10.8 g/10 minand a Melt Index of 0.34 g/10 min.

The copolymers produced in Polymerization Examples 5 and 6 were combinedinto one product sample.

Catalyst Preparation Example 4

51.5 g of a titanium catalyst component (prepared in the same manner asin Catalyst Preparation Example 3 above) was added to a one liter roundbottom flask containing a magnetic stir bar, followed by approximately500 ml of dry isohexane. 1.35 g ofdimethylsily(cyclopentadienyl)(9-fluorenyl)zirconium dichloride wasplaced in a small glass bottle and then 72.0 grams of amethylalumoxane/toluene solution which contained 13.4 wt % Al was addedthereto. The Zr compound/MAO solution was shaken and then 65 g of thissolution was transferred to an addition funnel. The addition funnel wasconnected to the one liter flask and the Zr/MAO solution was addeddropwise (over 10 minutes) to the flask while the contents of the flaskwere stirred. After this addition, the contents of the flask werestirred at room temperature for 70 minutes and then the flask was placedin an oil bath (45-55° C.) and solvents were removed with a nitrogenpurge over 5.7 hours. 76 g of a purple solid were isolated whichcontained 10.7 wt % Al; 0.95 wt % Mg; 1.21 wt % Ti, and 0.26 wt % Zr.

Catalyst Preparation Example 5

315 g of a titanium catalyst component (prepared in the same manner asin Catalyst Preparation Example 3 above) was added to a one-gallon glasscatalyst preparation vessel containing a double helix stirrer and fittedwith a heating jacket. Next, approximately 1575 ml of dry isopentane wasadded to the glass vessel. Then, under an inert atmosphere, 8.20 g ofdimethylsilyl(cyclopentadienyl)(9-fluorenyl)zirconium dichloride wasadded to a one-liter glass bottle, followed by 440 grams (480 ml ofsolution) of a methylalumoxane/toluene solution which was 4.56 Molar inAl. The Zr compound/MAO solution was shaken and then this solution wastransferred to a stainless steel Hoke bomb. The Hoke bomb was connectedto the one-gallon glass preparation vessel and the Zr/MAO solution wasadded at room temperature in small aliquots (at one minute intervalsover 28 minutes) to the glass preparation vessel while the contents ofthe vessel were stirred. After this addition, the contents of the flaskwere stirred at room temperature for about 5 hours and then the glassvessel was heated to about 45° C. and solvents were removed with anitrogen purge over about 14 hours. 340 g of a purple solid wereisolated.

Preparation of Ethylene/1-Hexene Copolymers in the Gas Phase

For Polymerization Examples 7-10, all work was performed in a continuousgas phase fluidized bed reactor, which can nominally produce copolymerat a rate of 3 pounds per hour.

Polymerization Example 7

Catalyst of Catalyst Preparation Example 4 was fed to the reactor at arate sufficient to produce copolymer at a rate of approximately 2.50pounds per hour. The reactor was operated at a total pressure ofapproximately 325 psia. Time averaged values for reactor compositionwere: ethylene 95.0 psi, 1-hexene 11.0 psi, hydrogen 8.5 psi, nitrogen210.5 psi. Reactor cycle gas mass flow rate was 1.2 kilopounds/h. Theresulting product had a density of 0.922 g/cm³ and a MI of 1.75 g/10min.

Polymerization Example 8

Catalyst of Catalyst Preparation Example 5 was fed to the reactor at arate sufficient to produce copolymer at a rate of approximately 2.75pounds per hour. The reactor was operated at a total pressure ofapproximately 335 psia. Time averaged values for reactor compositionwere ethylene 140.0 psi, 1-hexene 4.2 psi, hydrogen 18.9 psi, nitrogen171.9 psi. Reactor cycle gas mass flow rate was 1.2 kilopounds/h. Theresulting product had a density of 0.932 g/cm³ and a MI of 0.55 g/10min.

Polymerization Example 9

Catalyst of Catalyst Preparation Example 5 was fed to the reactor at arate sufficient to produce copolymer at a rate of approximately 2.40pounds per hour. The reactor was operated at a total pressure ofapproximately 330 psia. Time averaged values for reactor compositionwere: ethylene 140.0 psi, 1-hexene 4.9 psi, hydrogen 18.9 psi, nitrogen166.2 psi. Reactor cycle gas mass flow was 1.2 kilopounds/h. Theresulting product had a density of 0.927 g/cm³ and a MI of 0.76 g/10min.

Polymerization Example 10

Catalyst of Catalyst Preparation Example 5 was fed to the reactor at arate sufficient to produce copolymer at a rate of approximately 3.4pounds per hour. The reactor was operated at a total pressure ofapproximately 335 psia. Time averaged values for reactor compositionwere: ethylene 145.0 psi, 1-hexene 7.0 psi, hydrogen 21.0 psi, nitrogen162.0 psi. Reactor cycle gas mass flow rate was 1.2 kilopounds/h. Theresulting product had a density of 0.922 g/cm³ and a MI of 1.19 g/10min.

Resin and blown film data for Polymerization Examples 3+4 and 5+6 plus acontrol produced from a conventional Ziegler-Natta catalyst are shown inTable II below. TABLE II Polym. Ex. No. 3 + 4 5 + 6 Control Blend MeltIndex (g/10 min) 1.5 0.45 0.9 Blend MFR (FI/MI) 25 28 25 Blend Density(g/cm³) 0.913 0.915 0.916 Film Properties (thickness 1.0 mil): Dart Drop(F50, ASTM 380 575 362 D-1709) MD Elmendorf Tear (g/mil) 243 265 313Haze (%) 13.3 12.4 17.5 Gloss@ 45 degrees 42.4 43.2 35.2 1% SecantModulus 24,000 27,000 24,500

The resins of Polymerization Examples 3+4 and 5+6 are unexpectedlybetter in both haze and gloss for their level of stiffness.

The superior balance of properties demonstrated for the copolymers ofthe above Polymerization Examples according to the invention may beattributed to the bimodal comonomer distribution, which resulted fromthe use of a non-single-site/single-site polymerization catalystcombination. The stiffness is provided by a higher density Ziegler (Ti)copolymer component while the toughness, tear and clarity are associatedwith the uniform comonomer distribution of the copolymer componentprovided by the zirconocene catalyst.

As evidence for the bimodal comonomer distribution, the CRYSTAFtechnique was used to characterize the copolymers of PolymerizationExamples 3+4 and 2. The plot for Polymerization Examples 3+4 and 2 isillustrated in FIGS. 5 and 6, respectively. The peak centered around atemperature of 80° C. comes from the Ziegler (Ti) catalyzed component ofthe copolymer, while the broader peak at around 40° C. represents thezirconocene catalyzed component. The CRYSTAF plot for the ZieglerControl (FIG. 7) on the other hand only shows a single peak at thehigher end of the temperature range.

Polymerization Examples 7-10 are all representations of this inventioncarried out in a single gas phase reactor. Resin properties are given inTable III below. TABLE III Density MI Polym. Ex. No. (g/cm³) (g/10 min)MFR  7 0.922 1.75 36.1  8 0.932 0.55 47.0  9 0.927 0.76 47.4 10 0.9211.19 47.9

The superior balance of stiffness for a given density in comparison toZiegler catalyzed copolymers is illustrated in FIG. 8. At a givendensity the copolymers of Polymerization Examples 7-10 provide higherflexural modulus (stiffness). Another aspect of this invention is shownin Table IV where the flexural modulus is compared with the Shore Dindentation hardness. The control data is for two Ziegler catalyzedcopolymers produced in the same reactor under similar conditions toachieve their respective densities. Note the unique and unexpectedrelationship for the copolymers of the invention where at a givenhardness (Shore D), these copolymers are stiffer or alternatively, at agiven stiffness are softer than the Ziegler-catalyzed copolymers. TABLEIV Density 1% Flex Shore D Polym. Ex. No. (g/cm³) (psi) (@ 10 sec)  70.922 68,000 48.84  8 0.932 86,800 54.92  9 0.927 74,300 51.54 10 0.92165,800 48.66 Ziegler 0.922 55,900 52.62 Control A Ziegler 0.926 67,40054.64 Control B

The copolymers of Polymerization Examples 7-10 and the Ziegler Control Awere converted into film on a lab-scale Brabender blown film line. Thefilm dart impact and tear strengths are shown in Table V. Compared tothe film of the Ziegler Control A, the films made from the copolymers ofthe present invention are lower in both of these properties. The resultsare not surprising given the higher melt index and/or higher density ofthe copolymers of the invention. Additionally, there is a significantdifference in density between the resin components coming from the Zrcatalyst and the resin component from the Ti catalyst, which is likewisecontributing to the poorer impact and tear strengths of the copolymersof Polymerization Examples 7-10. Such a density discrepancy would beexpected to lead to incompatibility of the two resin components. Thisincompatibility would account for the diminished impact and MD tearstrengths because the Zr-derived copolymer component is not interactingor toughening the Ti-derived copolymer component. TABLE V Gauge DartImpact MD Tear TD Tear Polym. Ex. No. (mil) (F50, g) (g/mil) (g/mil)Ziegler 1.48 408 416 443 Control A  7 1.66  96 107 314  8 1.53  92 125303  9 1.57 140 191 641 10 1.29 196 126 156

Tensile data is shown in Table VI. Higher ultimate elongations and lowertensile break strengths were observed for the copolymers of theinvention relative to Ziegler Control A. Again these trends suggest thepresence of a very low density copolymer in the copolymers according tothe invention, since it is generally known to those skilled in the art,that as density decreases, elongation increases and tensile breakstrength decreases. TABLE VI Ultimate Tensile Strength Polym. MD/TDElongation MD/TD Break Ex. No. (%) (psi) Ziegler 832/552 7,130/6,150Control A 7 868/833 4,010/3,700 8 699/924 5,170/3,860 9 877/7624,730/2,370 10  813/934 4,140/2,920

This unusual balance of properties is again attributed to the uniquepolymer architecture of the copolymers of the invention. It isremarkable that such copolymers can be made in, e.g., a single slurry orgas phase reactor as opposed to blending and/or the use of dualreactors.

All patents, test procedures, and other documents cited herein,including priority documents, are fully incorporated by reference to theextent such disclosure is not inconsistent with this invention and forall jurisdictions in which such incorporation is permitted.

While the present invention has been described and illustrated byreference to particular embodiments, it will be appreciated by those ofordinary skill in the art, that the invention lends itself to manydifferent variations not illustrated herein. For these reasons, then,reference should be made solely to the appended claims for purposes ofdetermining the true scope of the present invention.

1. An ethylene/α-olefin copolymer comprising at least a first componentproduced by a non-single-site polymerization catalyst and a secondcomponent produced by a single-site polymerization catalyst, wherein theweight ratio of the first component and the second component ranges from9:1 to 1:9, wherein the copolymer has an α-olefin content of 5 to 20percent by weight, and wherein the copolymer shows at least one of (a)at least two CRYSTAF peak temperatures which differ by at least 15° C.and (b) at least two DSC melting peak temperatures which differ by atleast 15° C.
 2. The copolymer of claim 1, wherein the copolymer showstwo DSC melting peak temperatures which differ by at least 20° C.
 3. Thecopolymer of claim 1, wherein the copolymer shows two CRYSTAF peaktemperatures which differ by at least 20° C.
 4. The copolymer of claim1, wherein the copolymer shows both at least two DSC melting peaktemperatures which differ by at least 20° C. and at least two CRYSTAFpeak temperatures which differ by at least 20° C.
 5. The copolymer ofclaim 4, wherein the difference in CRYSTAF peak temperatures is at least25° C.
 6. The copolymer of claim 2, wherein the difference in CRYSTAFpeak temperatures is at least 30° C.
 7. The copolymer of claim 3,wherein the copolymer shows at least one DSC melting peak temperature inthe range from 115° C. to 135° C.
 8. The copolymer of claim 7, whereinthe copolymer shows at least one CRYSTAF peak in the temperature rangefrom 75° C. to 95° C.
 9. The copolymer of claim 4, wherein the weightratio of the first component and the second component ranges from 8:2 to2:8.
 10. The copolymer of claim 5, wherein the weight ratio of the firstcomponent and the second component ranges from 7:3 to 3:7.
 11. Thecopolymer of claim 3, wherein the copolymer has an α-olefin content ofat least 7 weight percent.
 12. The copolymer of claim 8, wherein thecopolymer has an α-olefin content of at least 10 weight percent.
 13. Thecopolymer of claim 1, wherein the copolymer has an α-olefin content ofat least 15 weight percent.
 14. The copolymer of claim 5, wherein theα-olefin comprises 3 to 12 carbon atoms.
 15. The copolymer of claim 7,wherein the α-olefin is selected from one or more of propene, 1-butene,1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and1-decene.
 16. The copolymer of claim 13, wherein the α-olefin comprises1-hexene.
 17. The copolymer of claim 15, wherein the copolymer has adensity of not more than 0.93 g/cm³.
 18. The copolymer of claim 4,wherein the copolymer has a density of not more than 0.925 g/cm³. 19.The copolymer of claim 16, wherein the copolymer has a density of notmore than 0.92 g/cm³.
 20. The copolymer of claim 1, wherein thecopolymer has an essentially unimodal molecular weight distribution. 21.The copolymer of claim 20, wherein the copolymer has been produced in asingle reactor.
 22. The copolymer of claim 21, wherein thenon-single-site polymerization catalyst is derived from at least onecompound selected from Ti and V compounds.
 23. The copolymer of claim22, wherein the single-site polymerization catalyst is derived from atleast one metallocene transition metal compound.
 24. The copolymer ofclaim 23, wherein the metallocene transition metal compound is selectedfrom Ti, Zr and Hf compounds.
 25. The copolymer of claim 24, wherein themetallocene transition metal compound comprises at least one compound ofthe general formula (II)CP_(X)MA_(y)  (II) wherein x is at least 2, M is selected from zirconiumand hafnium, Cp is selected from optionally substituted cyclopentadienyland optionally substituted cyclopentadienyl that is part of an aromaticpolycyclic ring system, provided that at least one Cp iscyclopentadienyl that is part of an aromatic polycyclic ring system, twocyclopentadienyl moieties may be linked by a bridging group, A isselected from halogen, hydrogen, hydrocarbyl and combinations thereof,and the sum (x+y) is equal to the valence of M.
 26. The copolymer ofclaim 25, wherein M represents zirconium.
 27. The copolymer of claim 26,wherein the aromatic polycyclic ring system is selected from optionallysubstituted indenyl and optionally substituted fluorenyl.
 28. Thecopolymer of claim 26, wherein x is 2 and the Cp groups are linked by abridging group.
 29. The copolymer of claim 28, wherein the bridginggroup includes at least one silicon atom.
 30. The copolymer of claim 1,wherein the single site polymerization catalyst is based on at least onecompound selected from ethylenebis(indenyl)zirconium dichloride anddimethylsilyl(cyclopentadienyl)(fluorenyl)zirconium dichloride.
 31. Thecopolymer of claim 27, wherein the metallocene transition metal compoundis used in combination with an alumoxane.
 32. An ethylene/1-hexenecopolymer comprising at least a first component produced by anon-single-site polymerization catalyst derived from a titanium compoundand a second component produced by a single-site polymerization catalystderived from a zirconium metallocene compound, wherein the copolymer hasa 1-hexene content of 6 to 12 percent by weight, wherein the weightratio of the first component and the second component ranges from 7:3 to3:7, wherein the copolymer shows (a) at least two CRYSTAF peaktemperatures which differ by at least 20° C. and (b) at least two DSCpeak temperatures which differ by at least 20° C., and wherein thedensity of the copolymer is not higher than 0.925 g/cm³, wherein thezirconium metallocene compound comprises two bridged cyclopentadienylrings, at least one of said cyclopentadienyl rings being part of anindenyl or fluorenyl moiety, the copolymer produced in a single reactor.33. A process for making an ethylene/α-olefin copolymer comprising atleast a first component and a second component, wherein the copolymerhas an α-olefin content of 5 to 20 percent by weight and wherein thecopolymer shows at least one of (a) at least two CRYSTAF peaktemperatures which differ by at least 15° C. and (b) at least two DSCpeak temperatures which differ by at least 15° C., said processcomprising contacting, in a single reactor, ethylene and α-olefin underpolymerization conditions and in the presence of hydrogen with acatalyst combination comprising at least one non-single-sitepolymerization catalyst and at least one single-site polymerizationcatalyst.
 34. The process of claim 33, wherein the copolymer has anα-olefin content of from 5 to 15 percent by weight.
 35. The process ofclaim 34, wherein the α-olefin comprises 1-hexene.
 36. The process ofclaim 33, wherein the single-site catalyst is derived from at least onemetallocene transition metal compound.
 37. The process of claim 36,wherein catalyst combination is used together with an alkylaluminumcocatalyst.
 38. The process of claim 33, wherein the catalystcombination comprises a support.
 39. The process of claim 38, whereinthe support comprises silica.
 40. The process of claim 34, wherein theprocess is carried out continuously.
 41. The process of claim 40,wherein the process is carried out in the gas phase.
 42. The process ofclaim 38, wherein the process is carried out as slurry polymerization.43. The process of claim 34, wherein the copolymer has a density of notmore than 0.925 g/cm³.
 44. The process of claim 39, wherein thenon-single-site polymerization catalyst is derived from at least onecompound selected from Ti and V compounds.
 45. The process of claim 36,wherein the at least one metallocene transition metal compound comprisesa compound of the general formula (II)Cp_(x)MA_(y)  (II) wherein x is at least 2, M is selected from zirconiumor hafnium, Cp is elected from optionally substituted cyclopentadienyland optionally substituted cyclopentadienyl that is part of an aromaticpolycyclic ring system, provided that at least one Cp iscyclopentadienyl that is part of an aromatic polycyclic ring system, twocyclopentadienyl moieties are linked by a bridging group, A is selectedfrom halogen, hydrogen, hydrocarbyl and combinations thereof, and thesum (x+y) is equal to the valence of M.
 46. The process of claim 37,wherein the at least one single-site polymerization catalyst is derivedfrom at least one of ethylenebis(indenyl)zirconium dichloride anddimethylsilyl-(cyclopentadienyl)(fluorenyl) zirconium dichloride.
 47. Anarticle made from the copolymer of claim
 1. 48. The article of claim 47,wherein the article is selected from blown and extruded articles.
 49. Afilm made from the copolymer of claim
 1. 50. The film of claim 49, whichhas a thickness of 0.2 to 10 mils.
 51. The film of claim 50, wherein thecopolymer contains up to 20 ppm transition metal derived from thedeactivated catalyst.
 52. A multilayer film comprising at least onelayer made from the copolymer of claim 4.